Authors: Tomalski, Michael; Leimkuehler, William; Schal, Coby; Vargo, Edward L.

Source: Annals of the Entomological Society of America, Volume 103, Number 1, January 2010 , pp. 84-95(12)

Publisher: Entomological Society of America

Abstract:

The chloro-nicotinyl insecticide imidacloprid is used extensively as a soil treatment against subterranean termites. We conducted the first study of the metabolic fate of imidacloprid in termites, by exposing workers of the eastern subterranean termite, Reticulitermes flavipes (Kollar) (Isoptera: Rhinotermitidae) to radiolabeled imidacloprid through topical application and ingestion. Several days after topical application, we detected up to 11 radiolabeled compounds. The parent compound, IMI, and the following six metabolites were identified by liquid chromatography/mass spectrometry: olefin-imidacloprid (major metabolite), 4/5-OH imidacloprid, 4,5-di-OH imidacloprid, des-nitro olefin imidacloprid, des-nitro imidacloprid, and a glucuronide conjugate of des-nitro imidacloprid (des-nitro IMI-glu). Over time, detoxification of imidacloprid proceeded from less polar to more polar compounds, with des-nitro IMI-glu seeming to be the ultimate, major end product in surviving termites. Degradation of imidacloprid was limited to internal tissues of the termite. Workers fed wood treated with imidacloprid or provided with a treated substrate (sand) had metabolitic profiles similar to topically treated termites. Termites fed imidacloprid or exposed to it in soil excreted detectable amounts of all of the identified metabolites. Finally, we determined that imidacloprid metabolites were less toxic to termites than imidacloprid itself. Only the olefin-imidacloprid and 5-OH imidacloprid caused morbidity in termites exposed to sand treated with these compounds, but at concentrations ≈10-20-fold higher than the parent imidacloprid. Our results shed light on the metabolic pathway used by termites to detoxify imidacloprid and show how metabolism plays a key role in determining the availability of the active ingredient and its various metabolites for transfer among workers within the colony.

Keywords: imidacloprid; termite; metabolism; Reticulitermes flavipes; toxicity

Document Type: Research article

Publication date: 2010-01-01

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• Annals of the Entomological Society of America is published in January, March, May, July, September, and November. Annals especially invites submission of manuscripts that integrate different areas of insect biology, and address issues that are likely to be of broad relevance to entomologists. Articles also report on basic aspects of the biology of arthropods, divided into categories by subject matter: systematics; ecology and population biology; arthropod biology; arthropods in relation to plant diseases; conservation biology and biodiversity; physiology, biochemistry, and toxicology; morphology, histology, and fine structure; genetics; and behavior.
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